The synthesis and isolation of heptafulvene (1) and sesquifulvalene (2) is reported: Acetoxy‐tropylium‐fluoroborate (10) may be prepared by addition of tropone to acetyl‐fluoroborate at low temperatures. The tropylium salt reacts easily with methyllithium and sodium cyclopentadienide to give the acetoxy‐methyl‐cycloheptatrienes 11 and the acetoxy‐cyclopentadienyl‐cycloheptatrienes 12 respectively. Gas‐phase pyrolysis of 11 and 12 affords in remarkably good yields heptafulvene (1) and sesquifulvalene (2), which are isolated in cristalline form at low temperatures. Spectroscopic as well as chemical evidence of the title compounds is presented.
Fulvenes are prepared by condensation of sodium cyclopentadienide with x‐acetoxy‐x‐chloro‐hydrocarbon derivatives, followed by elimination of acetic acid with triethylamine. The yields are approximately 60% for 6‐alkylfulvenes and similar to those of the classical synthesis for 6, 6‐polymethylenefulvenes. The reaction is carried out at low temperatures and under water‐free conditions. The purification of the fulvenes is simple.
The new phloroglucinol derivative 1 has been isolated from the light petroleum ether extract of the aerial parts of Hypericum calycinum. Its structure has been established by means of 1H- and 13C-NMR spectroscopy and by nOe, MHQC, and HMBC experiments on its monomethyl ether derivative 3. Compound 1 was fungicidal against Cladosporium cucumerinum in a TLC bioassay. In addition, this new phloroglucinol derivative was also found to exert an interesting antimalarial activity in an in vitro test system.
Tasmanine, a New Indole Alkaloid from Aristoteliapeduncularis (LABILL.) HOOK. F.
SummaryThe new indole alkaloid tasmanine (3) was isolated f;om Aristofelia peduncularis. Its relative configuration was elucidated on the basis of spectroscopic data (mainly NMR. spectra). It is closely related to the other known alkaloids from Aristotelia with double substitution at the indole nucleus. A biosynthetic pathway to these related natural compounds is proposed; also a biogenetic numbering system is suggested.Another representative of this group of alkaloids, aristoteline (2), was also isolated from A. peduncularis. This natural compound has previously been isolated from A . serrata and A . chilensis. Tasmanien beheimatete Pflanze Aristotelia peduncularis (LABILL.) HOOK. F. (Elaeocarpaceae) ist seit ca. 1970 Gegenstand chemischer Untersuchungen [2]. Bisher wurden neben dem Hauptalkaloid Peduncularin [2] die drei Nebenalkaloide Sorellin [3], Hobartin [3] und Aristoserratin (1) [4] isoliert und ihre Strukturen aufgeklart. Aus Nebenfraktionen konnten zwei weitere Basen isoliert werden, deren eine sich als identisch mit dem aus A . serrata W.R.B. OLIVER (aus Neuseeland) IS] gewonnenen Alkaloid Aristotelin (2) erwies (vgl. exper. Teil). Aristotelin wurde auch aus A . chilensis (MoL.) STUNTZ (aus Chile) isoliert [613). Die Struktur der anderen Pflanzenbase, Tasmanin (3), konnte mit spektroskopischen Methoden aufgeklart werden, woruber nachfolgend berichtet wird. I) 180. Mitt. s. 111. 2, 3, Teil der geplanten Dissertation von R . K., Universitat Zurich. Die absolute Konfiguration von ( + )-Aristotelin (2) aus A . serrum wurde durch Rontgenstrukturanalyse ermittelt [S]. (+ )-Aristotelin aus A . peduncularis wurde mit demjenigen aus A . serrata identifiziert (inklusive CD.-Spektren). Das aus A . chilensis isolierte Aristotelin ergab einen negativen spezifischen optischen Drehwert [6]; ob es sich dabei tatsachlich um den Antipoden zu ( + )-2 handelt, wurde unseres Wissens bisher nicht abgeklart. 86
Die in
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.